1. Field of the Invention
The present invention relates to a forward discrete/inverse-discrete Fourier transform device and method for optical orthogonal frequency division multiplexing (OFDM) communication and a transmitting and receiving apparatus comprising the device, and more particularly, to a forward discrete/inverse-discrete Fourier transform device and method for optical OFDM communication that enable a transmitting stage of an optical OFDM communication system to optically produce optical OFDM symbols and a receiving stage to demultiplex the symbols, and a transmitting and receiving apparatus comprising the device.
2. Discussion of Related Art
In general, a fast Fourier Transform (FFT) is an algorithm for use in digital signal processing to convert N sample points in a time domain into a corresponding N sample points in a frequency domain.
Orthogonal frequency division multiplexing (OFDM) refers to a multi-carrier scheme for splitting data into several data, modulating the data, and transmitting the modulated data in parallel. Subcarriers are obtained using a discrete Fourier transform (DFT) device.
FIG. 1 is a block diagram illustrating a conventional system for producing and processing OFDM symbols in a conventional optical communication system.
Referring to FIG. 1, an OFDM symbol is produced by an electronic inverse FFT: The inverse FFT is used to multiplex low-rate data with a multi-carrier defined as an orthogonal frequency component.
In a receiver, a photodetector converts a received optical OFDM symbol into a corresponding electrical waveform for an electronic FFT. A result of performing the FFT provides data transmitted with each carrier.
However, a conventional system requires a process of converting an electric signal into an optical signal and then the optical signal into the electric signal in order to process and produce OFDM symbols. This limits performance of an optical communication system.